This program project contains four projects, each focusing different aspects of T cell recognition relevant to autoimmunity. The project includes 7 investigators with experience in T cell immunity. Project I is an attempt to identify the antigen or antigens that trigger autoreactive T cells in Insulin Dependent Diabetes Mellitus. It attempts this in the NOD strain of mice and in humans with IDDM. It includes cellular and biochemical approaches, as well as approaches using molecular biology. Project II is an attempt to understand the biochemical and cellular basis of autoimmune myocarditis. Using primarily the model of myocarditid triggered by immunization with heart myosin, the purpose will be to identify the antigenic epitopes and how they are presented to T cells, Project III examines a model of transgenic mice that express the influenza virus hemagglutinin in their beta cells of the islets of Langerhans and which become diabetic. The cellular basis of injury and the biochemistry of recognition will be examined. Project IV examines the basic response of T cells in secondary lymphoid organs from mice expressing a transgene for a known T cell receptor to a peptide from ovalbumin. This is an ideal model to give new insights into the conditions that induce immunity or tolerance.